An Architect’s Tips on How to Save Money When Building An Extension

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Written by Taylan Tahir

Through our experience as residential architects working with homeowners on numerous projects, we have a few learnings to share.

In this article we present 12 tips to reduce the overall cost of your extension and help save some money along the way:

1. Plan ahead

It really pays to plan ahead. Right from the outset of a project, the more information you have in your possession, the more informed your decisions will be.

There is a sliding scale for the cost of changing your mind. It is cheaper to make design changes towards the beginning of the project than later on.

For example, you decide you would like to use a timber cladding instead of brick on the exterior face of your extension.

During RIBA Stage 2 – Concept Design this would be a minor change. It would involve additional time from the architect to visualise the new material in 3D and update 2D drawings to reflect the change.

The same decision made during RIBA Stage 4 – Detailed Design would necessitate updating 2D drawings, possibly 3D visuals as well as a new application to vary your planning permission (possibly delaying the programme). At this stage the setting out and spacing of fenestration and other external components is also based on cladding sizes and would need consideration. A seemingly small design change can have far-reaching, knock-on effects.

If you decided to change the cladding during RIBA Stage 5 – Construction, it would still be possible but would involve all of the above as well as an instruction for a ‘variation’ of the construction contract. It is possible this could add delays to the programme, adding to the overall costs.

By planning in detail, you’ll understanding exactly what you are paying for. By making every decision you can prior to beginning construction, you’ll reduce the chance of costly variations occurring further down the process.

Simple full width rear extension at Barnsbury House with a reduced materials palette of brick and stone.

2. Keep it simple

The more straightforward the design is the cheaper it will be. Simple.

In mathematical terms, this could mean reducing the overall perimeter of a building, which in turn reduces the amount of new external walls that would need to be constructed. Consider simple roof forms and selective use of glazing.

Pared back and modest doesn’t mean an unambitious design. Often the simplest solutions are the best ones.

3. Client supply items

Every item falling under the main contract will be subject to the contractor’s overheads and profits. This can add 10-20% mark up on top of the material cost of those items.

If you are happy to manage the process of selecting, ordering and delivering some of your own items to site you can define these as “client supply”. By taking on this responsibility you’ll be able to make savings on the contractor mark up.

In these instances, items such as kitchens, sanitaryware, floor finishes etc would fall outside of the main contract. This is especially common with kitchens, a high value item in any building contract.

Whilst this is a method to making savings, it can be a double-edged sword. It is important to be both accurate and timely with any client supply items. If delays are caused to the construction programme due to inaccurate quantities or delayed delivery to site, the contractor is entitled to claim for an extension of time to the construction programme and to recoup associated costs.

Kitchens at Melville Avenue are designed with budget in mind to use proprietary carcasses and bespoke plywood door fronts.

4. Adapt off the shelf or proprietary products

We love to design bespoke furniture, joinery and fittings specifically for our projects. They are beautiful, fit perfectly and will be totally unique but they do come at a cost. Where budget is a factor, areas of bespoke design should be prioritised to key areas of the project.

An alternative approach to specifying bespoke items is to modify off the shelf products. A good example of this is using proprietary kitchen carcasses such as Ikea or Howdens and adding bespoke fronts. This is a great way to save money on your kitchen but ensure you have control over the final look.

5. Move out during construction

The first instinct is often to remain at home throughout the construction of your extension. In theory, this would allow you to keep an eye on the construction works and make sure things are ticking along as well as saving you the costs of moving out temporarily.

In our experience it tends to make projects more complicated when homeowners remain living at the property. Contractors add the costs of the additional time needed to clean up thoroughfares such as hallways at the end of each day. Particular areas of the house that are part of the building site will need to be sectioned off. This will slow down the speed of work and the add to the length of the programme. Ultimately there is greater risk for contractors working on a house that the occupants remain living in, and risk is always factored into the cost of a building contract.

6. Experienced/Reputable Project Team

The cost of consultants can seem high before you’ve even started laying a brick. Working with an experienced project team is recommended and will actually save you money in the long run. There are many hidden pitfalls with construction projects and having an experienced team around you will minimise the risk of costs spiralling along the way.

An example of this value is working with a QS or Architect during construction to administer the building contract and assess monthly valuations. By doing this you ensure you are only ever paying for the work a contractor has completed at any given time and will prevent you from overspending.

7. Experienced/Reputable Contractor

At the point of signing a building contract with a main contractor you want to be confident they are offering you good value for money and they will deliver on their promise.

The lowest tender price is always the most enticing. However, rigorous tender analysis and due diligence is the key to ensuring all costs have been accounted for and the chosen contractor is going to be able to deliver your project on time and on budget. Choosing the wrong contractor can be costly so if you are working with an architect ensure they have interrogated the contactor and their pricing document before agreeing the construction contract.

Our Black Box extension was delivered with a phased approach with the first floor to be construction first.

8. Phased approach

If you are short of funds but are set on delivering the overall ambition of your project without compromising on the design, consider phasing work over a longer period of time. We would consider removing works such as external landscaping, cosmetic interior finishes or even finishes to secondary rooms from the contract to save on costs in the short term.

However, this can be a double-edged sword. Due to economies of scale, the more works you can include in your building contract the cheaper the overall price will be per square metre. Leaving a secondary part of the works until later can mean paying a premium for that smaller project.

9. Time

Ensure there is no reason for the project to overrun. Fundamentally, a contractor is entitled to charge additional prelim costs for any delays to the construction contract caused by the client. This may include lengthy party wall agreements not finalised pre-construction or delayed client supply items.

10. Re-use and recycle existing materials

Re-use of existing materials removed as part of the demolition work associated with your project is not only a great way to save money on buying new but is also more sustainable and will reduce the embodied carbon of your project. Look for opportunities to re-use masonry for external or retaining walls or existing timber floors can also be sanded, reoiled and re-laid.

11. Trade discount

When buying items of furniture, fixtures or fittings some suppliers offer a trade discount applicable to architects and construction professionals. Ask your architect if they would be willing to purchase on your behalf either for a small admin fee or by offering to share the trade discount.

12. Limit the relocation of services

When designing a new layout for your home it can seem simple on paper to squeeze in an additional bathroom or move the kitchen to a better location. There is always an associated cost with this and, depending on the existing floor structure and location of underground drainage, it can be more complicated than expected. Generally, retaining bathrooms and kitchens in similar locations where possible will save you money on your project.

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